I. Field of the Invention
This invention relates to communications systems. Specifically, the present invention relates to transceivers used in communications networks.
II. Description of the Related Art
Cellular telecommunications systems are characterized by a plurality of mobile transceivers in communication with one or more base stations. Each transceiver includes a transmitter and a receiver.
In a typical transceiver, an analog radio frequency (RF) input signal, received by an antenna, is downconverted by an RF section to an intermediate frequency (IF). Signal processing circuits perform noise filtering and adjust the magnitude of the signal via analog automatic gain control (AGC) circuitry. An IF section then mixes the signal down to baseband and converts the analog signal to a digital signal. The digital signal is then input to a baseband processor for further signal processing to output voice or data.
Similarly, the transmitter receives a digital input from the baseband processor and converts the input to an analog signal. This signal is then filtered and upconverted by an IF stage to an intermediate frequency. The gain of the transmit signal is adjusted and the IF signal is upconverted to RF in preparation for radio transmission.
In both the transmit and receive sections, signal gain adjustment and mixing is typically performed in the analog domain. This necessitates the use of a plurality of local oscillators (LOs) for signal downconversion, upconversion, and mixing. Analog local oscillators tend to be bulky and require the use of one or more phase-locked loops. As is well known in the art, phaselocked loops are large, expensive circuits that consume a considerable amount of power. Hence the use of PLLs, drive up the cost, size and power consumption of analog local oscillators and the transceivers in which these circuits are employed.
Hence, a need exists in the art for a cost-effective, space-efficient transceiver with low noise characteristics and minimal power consumption.